To measure corner sharpness we photographed
the standard ISO 12233 test chart with each camera set to its best quality
JPEG settings. We used the lenses at their widest and longest focal lengths
and with various apertures in Aperture Priority mode. The crops are taken
from the lower left corner of the chart and presented here at 100%.

There's some softness in the R1's corners at wide angle with the aperture
wide open, but closing it slightly produces much sharper results. The lens
is sharp at 120mm even when wide open. Note the Fujifilm and Panasonic cameras
have a 4:3 aspect ratio, hence the different cropped area.